What Is A Hot Asphalt Mix Plant

Hot Mix Asphalt Mixing Plant Facilities Mainly Composed:

1. Cold feeding system:

The cold material conveying system is composed of several separate cold material units, including silo vibrator, belt feeder, aggregate belt conveyor and main feeding belt.The single cold bin is equipped with a belt feeder with a frequency control motor, ‘feeding the aggregate belt through it’ and then feeding the belt to the drying cylinder.The conveyance of each belt conveyor is directly proportional to its rotating speed. The speed of the belt feeder is controlled by the computer control system by changing the frequency of the reducer to reach the amount of output. An alarm sensor is installed at the outlet of each cold bin.

2. Main belt conveyor:

The main belt conveyor is a component connecting the cold bin and the drying cylinder (commonly known as the inclined belt).

MITNIK Hot Mix Asphalt Mixing Facilities

3. Drying cylinder:

Drying cylinder is one of the main parts of asphalt mixture stirring.Its main function is to heat and dry the aggregate and heat the aggregate to the required temperature of the high quality asphalt mixture.The drying cylinder is a heat source provided by the burner to vaporize the moisture in the aggregate and drawn out by the draught fan.In the longitudinal direction of the drying cylinder, there is 3-5 degrees of inclination, the aggregate is inclined downward, and the flame and smoke of the burner are inclined upward, that is, reverse-flow.As the heat is absorbed by the aggregate, the temperature decreases gradually when the flue gas gradient increases.When the aggregate is inclined downward, the gradient of the aggregate is uniform.The speed of the drying cylinder is constant, and the drying cylinder is composed of several kinds of blades, such as long cylindrical body, friction ring, friction roller, speed reduction motor, roller bottom frame, feed end seat, limit wheel and heat preservation material.

4. Dust removal device:

The dedusting device is composed of first class gravity dedusting and second class bag dedusting.The bag filter is made of organic fiber and inorganic fiber tissue to filter the dust.Overheat protection: the working temperature of the bag filter is measured by the thermocouple at the entrance of the filter and displayed in the control room.When the temperature measured by the thermostat reaches the predetermined maximum of 180 degrees, the burner will stop working.Negative pressure device: a negative pressure device is installed between the inlet and outlet of the bag filter, showing the load loss of the filter.The load loss is mainly caused by dust concentration on the outer surface of the cloth bag.

Cleaning cycle: bag dust collector can be divided into multiple bag partitions.In the cleaning stage, the negative pressure in the dust collector will force the air from the outlet of the cloth bag to the inlet, so the cloth bag will swell, and the dust deposited on the cloth bag will fall into the hopper.The screw conveyor located in the hopper transports the dust to a designated location for uniform handling.The operation of covering the bulkhead is performed through the solenoid valve connected to the PLC by the cylinder, and the frequency and duration of atmospheric backblow is adjusted on the PC control panel.By separating the bag compartment from the air vents, external air can enter and vibrate the bag effectively.

5. Hot aggregate lifting, screening and storage system:

The aggregate discharged from the drying cylinder is lifted into the screening device by the hoist.The hot aggregate elevator adopts the guide hopper and gravity discharge.Low chain speed reduces wear and noise.As the hoist may stop during operation, the hoist is equipped with anti-reversing mechanism (the driving motor is equipped with a brake).

The vibrating screen and the hot aggregate storage bin are special devices of the forced stirring equipment, and the sieving device is the aggregate of different specifications mixed together after drying and heating through the drying cylinder, which is separated again according to the size of particle and stored separately in the storage chamber of the storage box, so as to accurately measure and gradate according to the requirements of the formula before stirring.Each storage bin has two big and small doors, which can more precisely control the speed of discharging and improve the measurement accuracy of aggregate.A high and low level material level sensor is installed in the hot bone material bin to transmit the material level information to the computer system.

Hot Asphalt Mixing Plant Equipment

6. Measurement and stirring system:

The measuring system is composed of asphalt scale, powder scale, aggregate scale, mixer and over-bucket.

A. Aggregate weighing: weighing hopper, weighing sensor, cylinder, weighing hopper door.

Each aggregate bin of the hot bin can be discharged into the weighing hopper through its own door.First is the hopper discharge with large aggregate, and last is the sand hopper discharge;In normal working environment, all metering operations are started automatically.The aggregate discharge of each aggregate is controlled by a dual-door electronic device of the size of the hot bin, which receives signals from the sensor which changes the amount of material to be discharged from each aggregate bin in proportion to the weight supplied.For example, if the aggregate weight of a bulkhead is assumed to be 120Kg, the automatic control will be used to control the weight increase in the hopper when the appropriate aggregate door is opened.When the added weight of aggregate is close to 120Kg, the hopper door will be closed (preset when the door is closed, and the small door is used to compensate the drop difference between the hopper door and the weighing hopper). When all the aggregate in the compartment is discharged into the hopper and reaches the set value, the hopper door will open and dump all the aggregate into the mixer at the same time.

B. Powder weighing: weighing hopper, weighing sensor, pneumatic butterfly valve and powder screw conveyor

The weighing of powder and the discharge of powder into the mixer are automatically controlled.The automatic weighing cycle of powder is basically the same as that of aggregate.The measured powder shall not be discharged at the same time as other aggregates, but shall be discharged into the mixer through a timer to delay the discharge of powder.The metering device consists of a weighing hopper and a screw.The screw conveyor can feed the powder directly into the mixer.In the case of two or three powder types, there will only be one weighing hopper powder feeding from the screw conveyor, other powder may have to exit the screw, or it will be imported.

Stone powder supply:

According to the engineering requirements, the stone powder in the asphalt mixture has a proportion of 5-7%.The supply device of stone powder includes storage bin and conveyor.The storage bin is a cylindrical structure with an inverted cone at the bottom.The top of the bin is provided with a level detection mechanism.In order to prevent stone powder from springing, a broken arch device is installed in the lower part of the powder chamber, which can be blown by vibrator or compressed air.The lower part of the silo is equipped with regulating valves and impeller feeder to control the output amount of stone powder. The stone powder discharged from the stone powder storage bin is delivered to the powder hopper for weighing by screw feeder, and the quantity is set and put into the mixer.The measurement of stone powder of this equipment adopts electronic scale, which is fed back to the computer system of control room directly by electronic sensor, and the quantity of stone powder is controlled.

C. Asphalt Weighing System:

Bitumen tank, three-way valve, two-way valve, asphalt filter, heat-conducting oil circulation pump, bitumen transfer pump, pneumatic three-way valve, asphalt scale, clamp pneumatic hard seal butterfly valve, asphalt self-flow pipe.

The bitumen pump is installed on the base of the bitumen tank. The bitumen pump can extract the bitumen and send it to the bitumen scale through the three-way valve.

When the weight (measured by Kg) of the filled asphalt is equal to the set value, the three-way valve changes position and the asphalt is transported to the asphalt tank (circulation).When the asphalt weighing begins to unload, the clamping pneumatic hard seal valve opens, and the asphalt will be discharged into the mixer from the self-flow tube. The asphalt weight is measured by three weighing sensors, and the electronic control device (similar to aggregate and powder) is transmitted synchronously.

Asphalt Drum Mixers Hot Mix Plants

D. Asphlat Mixer

When the weighing of aggregate, powder and asphalt is finished, the aggregate and other ingredients are fed into the mixer through automatic control.Automatic discharge of other ingredients (usually: aggregate, asphalt, powder) is allowed only after first feeding the aggregate.

1. The mixer of the equipment is double-shaft and double-drive, and the axial mounted low-speed synchronous mixer is used.

2. Main structure: lubricating device, mixing cylinder shell, lining lever device, stirring system, transmission system, shaft end device and door opening mechanism.

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Post time: Aug-24-2018
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